The guy who delivers the rat droppings is the unseen person who delivers rat droppings to the hot dog vendor that worked across the street from Fry and Bender's Popplers stand. In an effort to take business away from the vendor, and boost their own business, Bender went across the street and, very loudly and visibly, pretended to be the guy who delivers the vendor's rat droppings (2ACV15). The customers, one of whom was Stephanie, walked away disgustedly, but the vendor astutely recognized that Bender was not the guy who normally delivered his rat droppings, and Bender proudly walked back to his stand.

Bender: Hey, Mac, where do you want those rat droppings you ordered?[A man throws his hot dog down and the people in the line cross the road to the Popplers stand.]Hot dog vendor: Wait a minute. You're not the guy who delivers the rat droppings!